Field of the Invention
Embodiments of the invention relate to a quantum rod, and more particularly, to a quantum rod film having a low driving voltage and an improved polarization property, and a quantum rod composition and a display device including the same.
Discussion of the Related Art
Recently, as the society has entered in earnest upon an information age, a field of display devices that represent all sorts of electrical signals as visual images has developed rapidly. Flat panel display device, such as a liquid crystal display (LCD) device, a plasma display panel (PDP) device, a field emission display (FED) device, and an organic light emitting diode (OLED) device, has been introduced.
On the other hand, use of a quantum rod (QR) to the display device has been researched or studied. Since the QR has high emitting efficiency and excellent reproducibility, the QR can be applied to various uses. For example, applications of the QR to an emitting diode for lightings and a light source or other elements for the LCD device have been researched.
The QR includes a nano-sized core particle of II-VI, III-V, I-III-VI, or IV-VI semiconductor particle and a shell covering the core particle.
Since extinction coefficient and quantum yield of the QR is very large in comparison to general dyes, the QR emits strong fluorescent light. In addition, by controlling a diameter of the QR, a wavelength of light emitted from the QR can be controlled.
The QR emits linearly-polarized light. Namely, the light from the QR has a linearly-polarized property along a length direction of the QR.
In addition, the QR has an optical property that is capable of controlling emission by an electric field applied from the outside. This may be referred to as stark effect.
On the other hand, to simplify a fabricating process of the display device including the QR, a solution process for the QR film is introduced. Namely, by fabricating the QR film by the solution process, e.g., an ink jet method, a dispensing method, a roll-to-roll method, or a spin-coating method, the fabricating process of the display device including the QR is simplified and a thickness uniformity of the QR film is improved.
For example, the ink jet process is adequate to form a fine pattern and can use a low viscosity solution, and a material loss is minimized.
To coat the QRs by the ink jet method, an ink formulation of the QRs is required. Namely, the QR ink should have viscosity of about 8 to about 30 cP and surface tension of about 20 to about 40 dyne/cm and low volatility, e.g., a boiling point above 280° C., for the ink jet process.
However, the polarization property is decreased in the QR film formed by the solution process. In addition, there is a problem of high driving voltage in the QR film formed by the solution process.